RELATED PARTY TRANSACTIONS AND SIGNIFICANT TRANSACTIONS WITH RBS - Schedule of Related Party Transactions Effect on Net Interest Income (Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Related Party Transactions Effect on Net Interest Income (Expense) [Line Items]
Interest expense	$ (76)	$ (64)	$ (16)
RBSG | Interest rate swaps
Schedule of Related Party Transactions Effect on Net Interest Income (Expense) [Line Items]
Interest income	$ 12
Interest expense		$ (27)	$ (146)